Lessons from a seashell: Days on Earth used to be shorter

by | Mar 18, 2020 | Earth, Our Solar System, Science | 0 comments

Fossil rudist bivalves (Vaccinites) from the Al-Hajar Mountains, United Arab Emirates. Credit: Wikipedia, Wilson44691

The kind of tidal effects that we see on WASP-76b affect orbits in fascinating ways. Here on Earth, we have a moon that is tidally locked so that we only see one side of the moon. This is because the more massive Earth was able to exert torques on the moon that brought it’s rotation into sync with its orbital period. The moon is trying to do the same to earth, but it’s smaller, so the process may take longer than our Earth will actually be pleasantly orbiting a normal Sun. Still, we can see hints that in the past the Earth’s days were far shorter, and now we have a pretty new example of just how short those days were. 70 Million years ago, at the end of the time of the dinosaurs, a bivalved mollusk captured the length of the day in the ridges in its shell. Using a laser beam to measure ridges too small for researchers to count with a microscope, this science team found that days appeared to be just 23.5 hours long and a year was 372 days long.

These day tracking ridges are giving scientists insights on how the tides, symbiotic relationships with photosynthesising critters, and other factors affected mollusk growth. It’s really cool to see research that hits so many different topics and we encourage you to go explore the links we have on DailySpace.org which discuss the bioscience of this story.

Link to Story on AGU.

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